14N NMR data from the kidney and liver have indicated that significant amounts (50 mM) of trimethylamines are present in these tissues. In the kidney medulla these concentrations reached 100 mM. This high concentration of trimethylamines has previously not been generally known and the role of these cations in the metabolism and osmotic balance of these cells is unknown. We have begun to develop alternate techniques to determine the constituents which make up total trimethylamine found in 14N NMR. The available methods to characterize the different trimethylamines such as betaine, choline, TMA, TMAO, phosphylcholine, glycerol-phosphorylcholine, etc. have proven to be very unsatisfactory especially with regard to betaine. We, therefore, are developing a new assay for these compounds based on the very high K+ electrode response to trimethylamines after separating the different trimethylamines on a Dowex ion exchange column.